Map information providing system and map information searching method

ABSTRACT

A map information providing system for providing map data to a terminal device via a data transmission path, includes: a first server, the first server including a first storage unit for storing map data; and a second server connected with the first server and the terminal device via a network, the second server including a second storage unit for storing the map data. The first server includes: a unit for producing map search table which designates at least one of the first storage unit, the second storage unit and a third storage unit in the terminal device, from which certain map data is to be obtained; and a unit for transmitting the produced map searching table to the terminal device to be stored in the terminal device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system which provides map informationvia an information transmitting means such as a network (the internet, aLocal Area Network (LAN) and the like).

2. Description of the Prior Art

Recently, people can obtain desired map information using terminaldevices. In one method, a user accesses a storage medium such as aCD-ROM on which map information is stored, and reads out the stored mapinformation therefrom to display it on a screen of the terminal device.

In another method, a network serving as an information transmissionmeans, such as the internet, is used to obtain map information. Thereare various kinds of information services provided via the internet,including a map information searching and displaying service. In theservice of this kind, the user can access a WWW server, which has a mapdatabase and is connected to the internet, to obtain desired mapinformation and display it on the terminal device. Specifically, whenthe user designates an address, a place name, a station name, a name ofvarious kinds of facilities, a shop name, and the like on the terminaldevice, map information of the designated place and the area aroundthere is displayed on the terminal device as picture information.Therefore, the user can see the displayed map information to easily knowthe position of the station, facility and the like of interest.

However, in the above-mentioned method using the storage medium such asa CD-ROM, if map information is revised, the user should get the storagemedium of the new version. In addition, such a storage medium inherentlyhas a limit in its storage capacity, and it is sometimes difficult orimpossible for the user to obtain desired map information if he or sheneeds map information of very broad area, such as world map, or verydetailed map information.

On the other hand, in the method using the internet, such problem doesnot occur because the map database of the WWW server generally storesvarious kinds of map data. However, since the user needs to access theWWW server via the internet and download desired map information (i.e.,picture data) to the terminal device, it takes certain period of time.Particularly, if the user wants map information of the area which he orshe frequently uses, e.g., map information around his or her home,office or client, etc., it is troublesome to connect with the internetand download map data every time the user needs it.

SUMMARY OF THE INVENTION

In view of the above mentioned problems, it is an object of the presentinvention to provide a map information providing system and a mapinformation searching method capable of quickly and efficientlyobtaining desired map information at a terminal device connected to anetwork such as the internet.

According to one aspect of the present invention, there is provided amap information providing system for providing map data to a terminaldevice via a data transmission path, including: a first server, thefirst server including a first storage unit for storing map data; and asecond server connected with the first server and the terminal devicevia a network, the second server including a second storage unit forstoring the map data, the first server including: a unit for producingmap search table which designates at least one of the first storageunit, the second storage unit and a third storage unit in the terminaldevice, from which certain map data is to be obtained; and a unit fortransmitting the produced map searching table to the terminal device tobe stored in the terminal device.

In accordance with the map information providing system thus configured,the first server produces map search table which designates at least oneof the first storage unit, the second storage unit and a third storageunit in the terminal device, from which certain map data is to beobtained. Then, the first server transmits the map search table to theterminal device and make the terminal device store the map search table.Therefore, the terminal device can refer to the map searching table todetermine the storage unit and access it to obtain the desired map data.

In a preferred embodiment, the map searching table may includeinstructions to obtain the map data of a first region from the thirdstorage unit, to obtain the map data of a second region broader than thefirst region from the second storage unit and to obtain the map data ofa third region broader than the second region from the first storageunit. Thus, the user can obtain the map data of relatively limitedregion from the third storage unit in the terminal device quickly, andobtain the map data of relatively broad region from the first or secondstorage unit via the network, thereby enabling quick and efficient mapproviding operation.

In another preferred embodiment, the map searching table may includeinstructions to obtain the map data of a first scale from the thirdstorage unit, to obtain the map data of a second scale larger than thefirst scale from the second storage unit and to obtain the map data of athird scale larger than the second scale from the first storage unit. Bythis, relatively rough map information can be quickly obtained from theterminal device. Also, the detailed map information, generally having alarge data capacity, is obtained from the first or second storage unitvia the network. Therefore, desired map information may be quickly andefficiently obtained without excessively or unnecessarily occupying thestorage capacity of the terminal device.

In a still another preferred embodiment, the map searching table mayinclude revision information indicating revision dates of the respectivemap data stored in the first storage unit, the second storage unit andthe third storage unit. Thus, by referring to the map searching table,the user can constantly obtain the map information of the newestversion.

According to another aspect of the present invention, there is provideda map information searching method executed in a map informationsearching method executed in a map information providing systemincluding: a first server including a first storage unit for storing mapdata; a second server connected with the first server via a network andhaving a second storage unit for storing the map data; and at least oneterminal device connected with the second server via the network andincluding a third storage unit for storing the map data and a mapsearching table which designates at least one of the first storage unit,the second storage unit and a third storage unit in the terminal device,from which certain map data is to be obtained, the method including thesteps of: at the terminal device, receiving from a user an inputdesignating map data to be searched for; referring to the map searchingtable and determining one of the first storage unit, the second storageunit and the third storage unit, from which the map data designated bythe user is to be obtained; accessing the storage unit determined by thedetermining step to obtain the designated map data; and displaying theobtained map data on a display device of the terminal device.

In accordance with the map information searching method, the map searchtable includes designations of at least one of the first storage unit,the second storage unit and a third storage unit in the terminal device,from which certain map data is to be obtained. Therefore, the terminaldevice can refer to the map searching table to determine the storageunit and access it to obtain the desired map data.

In a preferred embodiment, the method may further include the steps of:storing the map data of a first region in the third storage unit,storing the map data of a second region larger than the first region inthe second storage unit and storing the map data of a third regionlarger than the second region in the first storage unit; and storing, inthe map searching table, information indicating one of the storage unitsin which the map data is stored. Thus, the user can obtain the map dataof relatively limited region from the third storage unit in the terminaldevice quickly, and obtain the map data of relatively broad region fromthe first or second storage unit via the network, thereby enabling quickand efficient map providing operation.

In another preferred embodiment, the method may further include thesteps of: storing the map data of a first scale in the third storageunit, storing the map data of a second scale larger than the first scalein the second storage unit and storing the map data of a third scalelarger than the second scale in the first storage unit; and storing, inthe map searching table, information indicating one of the storage unitsin which the map data is stored. By this, relatively rough mapinformation can be quickly obtained from the terminal device. Also, thedetailed map information, generally a having large capacity, is obtainedfrom the first or second storage unit via the network. Therefore,desired map information may be quickly and efficiently obtained withoutexcessively or unnecessarily occupying the storage capacity of theterminal device.

In still another preferred embodiment, the method may further includethe step of storing, in the map searching table, revision informationindicating revision dates of the respective map data stored in the firststorage unit, the second storage unit and the third storage unit. Thus,by referring to the map searching table, the user can constantly obtainthe map information of the newest version.

According to still another aspect of the present invention, there isprovided a map information searching method executed in a mapinformation providing system including: a first server including a firststorage unit for storing map data; a second server connected with thefirst server via a network and having a second storage unit for storingthe map data; and at least one terminal device connected with the secondserver via the network and including a third storage unit for storingthe map data, the method including the steps of: a first step forreceiving from a user, at the terminal device, an input designating mapdata to be searched for; a second step for determining whether or notthe designated map data is stored in the third storage unit; a thirdstep for accessing the third storage unit to obtain the designated mapdata if it is determined in the second step that the designated map datais stored in the third storage unit; a fourth step for determiningwhether or not the designated map data is stored in the second storageunit if it is determined in the second step that designated map data isnot stored in the third storage unit; a fifth step for accessing thesecond storage unit to obtain the designated map data if it isdetermined in the fourth step that the designated map data is stored inthe second storage unit; a sixth step for determining whether or not thedesignated map data is stored in the first storage unit if it isdetermined in the fifth step that the designated map data is not storedin the second storage unit; a seventh step for accessing the firststorage unit to obtain the designated map data if it is determined inthe sixth step that the designated map data is stored in the firststorage unit; and an eighth step for displaying, on a display device ofthe terminal device, the map data obtained in one of the third step, thefifth step and the seventh step.

In accordance with the map information searching method, storageposition of the designated map data is automatically determined to beone of the first to third storage units, and the map data can beobtained by accessing the storage unit thus determined.

The nature, utility, and further features of this invention will be moreclearly apparent from the following detailed description with respect topreferred embodiment of the invention when read in conjunction with theaccompanying drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of a mapinformation providing system according to the embodiments of the presentinvention;

FIG. 2 shows an example of an initial display of a map searchingprogram;

FIG. 3 shows an example of a display of the map searching program at amap search input stage;

FIG. 4 shows an example of a map searching table according to the firstembodiment of the present invention;

FIGS. 5A to 5C show examples of map searching tables according to thesecond embodiment of the present invention;

FIGS. 6A and 6B show other examples of map searching tables according tothe second embodiment of the present invention;

FIG. 7 shows an example of a map searching table according to the thirdembodiment of the present invention; and

FIG. 8 is a flowchart showing a map searching method according to thefourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will now be describedbelow with reference to the attached drawings.

[A] System Configuration

FIG. 1 shows a schematic configuration of a map information providingsystem according to the present invention. As shown, the map informationproviding system includes a WWW server 10 and a LAN 6, both of which areconnected to the internet 7.

The WWW server 10 is a center for carrying out the map informationproviding service on the internet 7, and includes a server 11 and a mapdatabase 12. The map database 12 stores position information (e.g.,coordinate information) on the map, such as latitude data and longitudedata as well as picture data of the map corresponding to those positioninformation (hereinafter referred to as “map data”). The map data has amultiple hierarchical structure in which multiple hierarchies correspondto map data of different scales. Namely, plural groups of map data ofdifferent scales, such as the whole Japan map, the prefecture level map,etc. are prepared. Specifically, the whole Japan or a certain area ofJapan is divided into plural regions in a mesh manner, and the map dataof each of the divided regions (hereinafter referred to as “map file”)is assigned with a map file name (i.e., classification number), thusclassifying the map data. Therefore, the map files are prepared forvarious scales, and each map file is specified by the map file name(e.g., region 1—1, region 1-2, . . . , region n-m) indicating the regionthus classified. It is noted that the details of the map data to bestored in the map database 12 will be described later with reference tothe embodiments.

The LAN 6 is connected to the internet 7 via a relay server 2, andterminal devices 1 and a local server 3 are also connected to the LAN 6.The local server 3 includes a server 4 and a local database 5. The localdata base 5 also stores map data, the detail of which will be describedlater.

Next, the description will be given of the method of obtaining map dataat the terminal device 1. In the map information providing systemaccording to the present invention, the map data is divided into threegroups and stored in three storage locations, i.e., the map database 12in the WWW server 10, the local database 5 in the local server 3 and thehard disk (not shown) in each terminal device 1. Accordingly, the useroperates the terminal device 1 to obtain desired map data from one ofthe three storage locations. Specifically, when obtaining mapinformation of the desired area, the user runs the map searching programin the terminal device 1. During the execution of this program, the userinputs or designates information relating to the desired area, and thescale of the map data corresponding to the designated area. The mapsearching program has a function to selectively access appropriate oneof the hard disk in the terminal device 1, the local database 5 and themap database 12, according to the user's inputs, to obtain thedesignated map data.

The examples of the input screen of the map searching program are shownin FIGS. 2 and 3. FIG. 2 shows an example of the initial display of themap information searching program. In FIG. 2, there is a map displayportion 30 at the upper area of the screen 2, wherein map picture isdisplayed. Just below the map display portion 30, there is a scaledesignation portion 32, which indicates the scale of the map displayedwithin the map display portion 30. The buttons in the scale designationportion 32 correspond to different scales (11 levels in this example).In the example shown in FIG. 3, the map picture is displayed with itssmallest scale (nearest to the Japan mark at its left side). In order tomagnify the displayed map picture, the user should click the button atright side (closer to the “street”) to display the map picture of largerscale. On the left of the scale designation portion 32, a scrollingportion 34 is displayed. The scrolling portion 34 is used to display themap picture of the area around the currently displayed area and includesthe arrows in eight directions from the currently displayed position. Ifthe user clicks the upward arrow in the scrolling portion 34, forexample, the map picture of the neighboring area in north direction ofthe currently displayed area appears on the map display portion 30.

Below the scale designation portion 32, there is provided an inputportion 36 used to designate and/or input the desired place to besearched for. On the left side of the input portion 36, buttons of“ADDRESSES”, “STATIONS” and “LANDMARKS” are shown. By clicking thosebuttons, a list of candidate addresses, station names or landmark namesappears. Then, the user can choose the desired candidate to display themap picture of that place. On the right side of the input portion 36,input boxes of address, station name and landmark name are displayed,and the user can input address and/or name of the desired place via aninput device such as a keyboard and/or mouse in the user terminal device1. For example, if the user inputs the station name “JR KAMATA Sta.” inthe station name box, the map picture around the JR KAMATA stationappears on the map display portion 30 as shown in FIG. 3. Thus, the userinputs, with watching the screen of the terminal device 1, informationrelating to the area to be searched for and the scale of the map to bedisplayed.

When the user inputs necessary information, the map searching programrefers to the map searching table stored in the terminal device 1. Themap searching table indicates one of the three storage locations, i.e.,the map database 12, the local database 5 and the hard disk in theterminal device 1, in which the map data designated by the user isstored. By referring to the this map searching table, the map searchingprogram accesses the designated storage location to obtain designatedmap data. Namely, if the map searching table designates the map database12 in the WWW server 10, the map searching program connects with theinternet 7 and accesses the map database 12 in the WWW server 10 todownload the designated map data to the terminal device 1. If the mapsearching table designates the local database 5, the map searchingprogram connects with the local server 3 via the LAN 6 and accesses thelocal database 5 to obtain and download the designated map data to theterminal device 1. If the map searching table designates the hard diskin the terminal device 1, the map searching program accesses the harddisk in the terminal device 1 to obtain the designated map data anddisplay it. Thus, the user obtains desired map data at the terminaldevice 1 and displays it on the screen of the terminal device 1.

Next, the description will be given of the contents of the map searchingtable. A novel feature of the present invention is that the map datawhich the user can obtain are appropriately distributed to and stored inthe three storage locations, i.e., the map database 12 in the WWW server10, the local database 5 in the LAN 6 and the hard disk in the terminaldevice 10 so that the user can access the appropriate storage location,by referring to the map searching table, to obtain the desired mapinformation. Now, the contents of the map searching table and the mapsearching process based on the contents will be described by referringto the first to third embodiments.

[B] 1st Embodiment

In the first embodiment, the map data which the user frequently usesand/or map data of relatively limited area is stored in the hard disk inthe terminal device 1. The map data for the area which is usedrelatively infrequently is stored in the local database 5. Further themap information which the user infrequently uses and/or map informationfor relatively broad are a is stored in the map database 12 in the WWWserver 10.

FIG. 4 shows an example of the map searching table according to thefirst embodiment. It is noted that FIG. 4 shows the example of the mapsearching table which is stored in a terminal device 1 which belongs toan in-house LAN 6 of a company located in Tokyo. As shown, in the mapsearching table, the map data inside of Tokyo, which is most frequentlyused from the terminal device 1m is stored in the hard disk of theterminal device 1, and the map data inside of Japan, which is secondlyfrequently used, is stored in the local database 5 of the local server3. The map data outside of Japan, which is infrequently used, is storedin the map database 12 in the WWW server 10. In addition, the mapsearching table indicating the storage locations of those map data isstored in the terminal device 1. It is noted that, in practice, the mapdata are specified by the name of the respective map files (e.g., region1—1, etc.) as described above. However, in FIG. 4, the respective mapdata are represented by the region names for the sake of convenience inthe description. Actually, in the column “REGION” in FIG. 4, the mapfile names corresponding to the respective regions are stored like FIGS.5 to 7.

At the time of searching the map information, when the user designatesthe map of certain region in Tokyo by operating the terminal device 1,the map searching program refers to the map searching table of FIG. 4,accesses the map data in the hard disk of the terminal device 1 toobtain the designated map data, and displays it on the screen of theterminal device 1.

Therefore, it is unnecessary to connect with the LAN 6 or the internet7, and the user can quickly obtain the desired map information. On theother hand, if the user searches for the map data of outside of Tokyo oroutside of Japan, the map searching program accesses the local server 5in the LAN 6 or the map database 12 in the WWW server 10 to obtain themap data. As a result, the user can quickly get the map informationwhich he or she frequently uses without connecting with the internet 7or the LAN 6. At the same time, since the map data stored in theterminal device 1 is limited to those which are frequently used or whichcorrespond to limited small areas, it may be possible to prevent thestorage area of the hard disk in the terminal device from beingunnecessarily occupied.

The map data to be stored in the hard disk of the terminal device 1and/or the local database 5 may be appropriately changed inconsideration of the user's access history. For example, the terminaldevice may store, with using the map searching program, theidentification information of the map file designated by the usertogether with the number of times the user accessed that map file, andchanges the storage location of the map data which is accessed morefrequently than a given reference, e.g., more than predetermined timesor a predetermined frequency (given times per month) from the furtherstorage location to nearer storage location from the user terminaldevice 1, e.g., from the WWW server 10 to the local server 3, or fromthe local server 3 to the user terminal device 1. Reversely, map filesinfrequently accessed may be moved to further storage location from theuser terminal device 1. With the aid of such change, if business with anew client starts and increases, for example, the map data around thenew client's office can be moved from the further storage location tothe user terminal device 1 to enable quick search.

[C] 2nd Embodiment

In the second embodiment, the map data of different scales for the sameregion are distributed to three storage locations, i.e., the mapdatabase 12, the local database 5 and the terminal device 1.Specifically, for the map of whole Japan, the hard disk of the terminaldevice 1 stores map data of smallest scale (i.e., roughest map), and thelocal database 5 stores map data of larger scale. The map database 12 inthe WWW server 10 stores map data of largest scale (i.e., most detailedmap).

FIGS. 5A to 5C show the contents of the map searching tables accordingto the second embodiment. As shown, the map searching tables areseparately prepared for different scales, and include designation of thestorage location storing the map files of respective regions. In theexample of FIGS. 5A to 5C, the map files of the scale {fraction(1/50000)} are all stored in the hard disk of the terminal device 1, themap files of the scale {fraction (1/25000)} are all stored in the localdatabase 5, and the map files of the scale {fraction (1/10000)} are allstored in the map database 12 in the WWW server 10. As mentioned above,when designating a desired region to be searched for, the useradditionally inputs information relating to the scale of the map file.Therefore, the map searching program refers to the map searching tablecorresponding to the scale designated by the user, and accesses thedesignated storage location to obtain the map file. By storing the mapdata of small scale in the terminal device 1, storing the map datalarger scale in the local database 5 and storing the map data of furtherlarger scale in the map database 12 of the WWW server 10, if it issufficient for the user to obtain relatively rough map data, the mapsearching program simply reads out the map file from the terminal device1 without accessing the LAN 6 and the WWW server 10. Therefore, the mapinformation can be quickly obtained. If the user needs more detailed mapdata, the map searching program accesses the local database 5 or the mapdatabase 12 according to the designated scale to obtain the map file. Ingeneral, since detailed map data of larger scale has larger informationamount than rough map data of smaller scale, it is preferred that thedetailed map data is stored in the local database 5 or the map database12 having large storage capacity. On the contrary, rough map data ofsmaller scale has generally smaller information amount, and hencestoring the rough map data in the terminal device 1 does not excessivelyoccupy the storage capacity of the terminal device 1.

In some regions (e.g., regions corresponding to forest or sea, etc.),map files of larger scale may not be prepared. In such a case, the mapsearching table indicates that the map file of that scale, correspondingto those regions, do not exist (see. FIG. 6A, region n-m). In that case,the map searching program may be designed to show the message notifyingthe user of the nonexistence of the map file of the corresponding scale.Alternatively, the map searching program may be designed to display themap file of one level smaller scale instead of the map data of thedesignated scale. For example, if the map file of the scale {fraction(1/25000)} for the region n-m does not exist in the example shown inFIG. 6A, the map file of the scale {fraction (1/50000)} for the regionn-m may be automatically obtained and displayed.

In addition, it is possible to store the map data of the same scale forthe same region at two different storage locations. For example, in theexample of the map searching table shown in FIG. 6B, for the regions 1-1and 1-2, the map data of the scale {fraction (1/50000)} is stored inboth the map database 12 in the WWW server 10 and the local database 5in the local server 3. In such a case, the map searching programnormally accesses the storage location nearer from the terminal device(i.e., the local database 5 in this case) and obtains the map file.Thus, by storing the same map data at two different storage locations,if one storage location becomes inaccessible due to some reasons, themap searching program can access the other storage location to obtainthe same map file, and hence the reliability of the system may beimproved. It is noted, however, that the consumption of the storage areain the storage location is doubled in that case. In this view, it ispreferred that such duplicate storage of the same map data isefficiently made for some special regions, for example, a commerciallyimportant region or a frequently accessed region, such as the centralregions in Tokyo.

While the above description discussed the map data of three differentscales, if the map data of larger number of different scales exist, theymay be classified into three groups in the order of those scales andstored in the three storage locations.

[D] 3rd Embodiment

The third embodiment is characteristic in that the revision informationof the map data is recorded in the map searching table so that the mapdata of the newest version may be constantly provided to the user. FIG.7 shows an example of the map searching table including the revisionhistory of the map files for plural regions. In FIG. 7, with respect tothe region 1-1, for example, the map data in the terminal device 1 wasrevised on Jan. 1, 1997, and the map data in the WWW server 10 and thelocal server 3 were revised on Jun. 1, 1997.

Normally, the map data in the WWW server 10 and the local server 3 arerevised first, and then the map data in the terminal device 1 isrevised, if necessary. In searching for the map data, when the userdesignates the desired region, the map searching program refers to therevision information in the map searching table shown in FIG. 7. Then,the map searching program accesses the storage location having newestrevision date for the designated region and obtains the newest map file.If the map data having the same revision date are stored in differentstorage locations (e.g., the regions 1-1 and 1-2 in FIG.7), the mapsearching program accesses the nearer storage location from the terminaldevice. In this example, the map searching program recognizes that themap data for the region 1-1 having the same revision date are stored inboth the WWW server 10 and the local server 3, and accesses the localserver 3, which is nearer from the terminal device 1 than the WWW server10, to obtain the map file.

The contents of the map searching table is revised by the WWW server 10in such a manner that the WWW server 10 10 distributes the revisioninformation to the respective terminal devices at the same time therevised version of the map files themselves are distributed to thestorage locations. By way of example, the WWW server 10 supplies the newmap file for the region 3-1 to the local server 3 on Jun. 1, 1997, andthen sends the revision information indicating that revision to therespective terminal devices 1 to change the contents of the revisioninformation in the map searching table of the terminal devices, i.e.,changes the revision date of the map file for region 3-1 stored in theWWW server 10 to Jun. 1, 1997. Further, if the map file for the region3-1 stored the WWW server 10 is further revised on Oct. 15, 1997, therevision information is distributed to the terminal devices 1 and therevision date of corresponding map file for the WWW server 10 arechanged to Oct. 15, 1997 in all terminal devices 1. Thus, the mapsearching tables in all terminal devices are revised every time when themap data is revised, and hence the user can obtain the map data of thenewest version from any terminal device 1. It is noted that plural mapsearching tables as shown in FIG. 7 may be prepared for the map data ofdifferent scales.

As an alternative of the third embodiment described above, a storagedevice may be prepared in each terminal device I which stores therevised map file itself as well as information as to the region of themap file, the scale, etc. when the map revision is made. If the userinstructs searching the map data of a certain region, the map searchingprogram refers to the revision information in the storage device firstof all, and displays the corresponding map data if it is stored in thestorage device. If the corresponding map data does not exist in thestorage device, the map searching program can obtain the map data fromother storage locations, such as the local database 5 or the mapdatabase 12. In that case, the map searching program receives therevision information from the WWW server 10 when the map revision ismade, and stores it in the storage device.

[E] 4th Embodiment

In the fourth embodiment, the map data is searched for without using themap searching table. FIG. 8 is a flowchart the search method accordingto the fourth embodiment. With the system configuration shown in FIG. 1,when the user designates the map data to be searched for via theterminal device 1 (step S1), the map searching program determineswhether or not the designated map data is stored in the hard disk of theterminal device 1 (step S2). If the determination results in YES, themap searching program accesses the hard disk and obtains the designatedmap data (step S3), and then displays the map data thus obtained on thedisplay screen of the terminal device 1 (step S4).

If the determination in step S2 results in NO, the map searching programconnects with the local server 3 via the LAN 6, and determines whetheror not the designated map data is stored in the local database 5 withinthe local server 3 (step S5). If the determination results in YES, themap searching program accesses the local database 5, and obtains thedesignated map data (step S6). Subsequently, the map searching programdownloads the map data to the terminal device 1 (step S7), and displaysit on the display screen of the terminal device 1 (step S4).

If the determination in step S5 results in NO, the map searching programconnects with the WWW server 10 via the LAN 6, the relay server 2 andthe internet 7, and determines whether or not the designated map data isstored in the map database 12 of the WWW server 10 (step S8). If thedetermination results in YES, the map searching program accesses the mapdatabase 12, and obtains the designated map data (step S9). Then, themap searching program downloads the map data to the terminal device 1(step S10), and displays it (step S4).

If the determination in step 8 results in NO, the map searching programdisplays a message, to the user, stating that the designated map datadoes not exist or cannot be obtained for some reasons (step S11).

The above method of the fourth embodiment may be modified such that themap searching program refers to the above mentioned map searching table.Namely, the map searching program may determine whether or not thedesignated map data is stored in the hard disk in the terminal device 1,and then in the local database 5 in the local server 3, and then in themap database in the WWW server 10, by referring to the contents of themap searching table.

According to the map searching method of the fourth embodiment describedabove, if the designated map data is stored in plural storage locations(e.g., in both the local database and the map database 12, or in boththe hard disk of the terminal device 1 and the local database 5), themap searching program may obtain the map data from the nearest storagelocation with shortest access time.

The invention may be embodied on other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description and all changeswhich come within the meaning an range of equivalency of the claims aretherefore intended to embraced therein.

The entire disclosure of Japanese Patent Application No. 10-147889 filedon May 28, 1998 including the specification, claims, drawings andsummary is incorporated herein by reference in its entirety.

What is claimed is:
 1. A map information providing system for providingmap data to a terminal device via a data transmission path, comprising:a first server, the first server comprising a first storage unit forstoring map data; and a second server connected with the first serverand the terminal device via a network, the second server comprising asecond storage unit for storing the map data, the first servercomprising: a unit for producing map searching table which designates atleast one of the first storage unit, the second storage unit and a thirdstorage unit in the terminal device, from which certain map data is tobe obtained; and a unit for transmitting the produced map searchingtable to the terminal device to be stored in the terminal device,wherein map data of regions of different scales are stored in differentstorage units and these data are accessed through the map searchingtable so as to optimize and minimize the time in which users access thenetwork.
 2. The system according to claim 1, wherein the map searchingtable includes instructions to obtain the map data of a first regionfrom the third storage unit, to obtain the map data of a second regionbroader than the first region from the second storage unit and to obtainthe map data of a third region broader than the second region from thefirst storage unit.
 3. The system according to claim 1, wherein the mapsearching table includes instructions to obtain the map data of a firstscale from the third storage unit, to obtain the map data of a secondscale larger than the first scale from the second storage unit and toobtain the map data of a third scale larger than the second scale fromthe first storage unit.
 4. The system according to claim 1, wherein themap searching table includes revision information indicating revisiondates of the respective map data stored in the first storage unit, thesecond storage unit and the third storage unit.
 5. The map informationproviding system according to claim 1, wherein users can quickly get mapdata which they frequently use by accessing the third storage unit inthe terminal device, without connecting to the first server or thesecond server.
 6. A map information searching method executed in a mapinformation providing system comprising: a first server comprising afirst storage unit for storing map data; a second server connected withthe first server via a network and having a second storage unit forstoring the map data; and at least one terminal device connected withthe second server via the network and comprising a third storage unitfor storing the map data and a map searching table which designates atleast one of the first storage unit, the second storage unit and a thirdstorage unit in the terminal device, from which certain map data is tobe obtained, said method comprising the steps of: at the terminaldevice, receiving from a user an input designating map data to besearched for; referring to the map searching table and determining oneof the first storage unit, the second storage unit and the third storageunit, from which the map data designated by the user is to be obtained;accessing the storage unit determined by the determining step to obtainthe designated map data; and displaying the obtained map data on adisplay device of the terminal device, wherein map data of regions ofdifferent scales are stored in different storage units and these dataare accessed through the map searching table so as to optimize andminimize the time in which users access the network.
 7. The methodaccording to claim 6, further comprising the steps of: storing the mapdata of a first region in the third storage unit, storing the map dataof a second region broader than the first region in the second storageunit and storing the map data of a third region broader than the secondregion in the first storage unit; and storing, in the map searchingtable, information indicating one of the storage units in which the mapdata is stored.
 8. The method according to claim 6, further comprisingthe steps of: storing the map data of a first scale in the third storageunit, storing the map data of a second scale larger than the first scalein the second storage unit and storing the map data of a third scalelarger than the second scale in the first storage unit; and storing, inthe map searching table, information indicating one of the storage unitsin which the map data is stored.
 9. The method according to claim 6,further comprising the step of storing, in the map searching table,revision information indicating revision dates of the respective mapdata stored in the first storage unit, the second storage unit and thethird storage unit.
 10. A map information searching method executed in amap information providing system comprising: a first server comprising afirst storage unit for storing map data; a second server connected withthe first server via a network and having a second storage unit forstoring the map data; and at least one terminal device connected withthe second server via the network and comprising a third storage unitfor storing the map data, said method comprising the steps of: a firststep for receiving from a user, at the terminal device, an inputdesignating map data to be searched for; a second step for determiningwhether or not the designated map data is stored in the third storageunit; a third step for accessing the third storage unit to obtain thedesignated map data if it is determined in the second step that thedesignated map data is stored in the third storage unit; a fourth stepfor determining whether or not the designated map data is stored in thesecond storage unit if it is determined in the second step thatdesignated map data is not stored in the third storage unit; a fifthstep for accessing the second storage unit to obtain the designated mapdata if it is determined in the fourth step that the designated map datais stored in the second storage unit; a sixth step for determiningwhether or not the designated map data is stored in the first storageunit if it is determined in the fourth step that the designated map datais not stored in the second storage unit; a seventh step for accessingthe first storage unit to obtain the designated map data if it isdetermined in the sixth step that the designated map data is stored inthe first storage unit; and an eighth step for displaying, on a displaydevice of the terminal device, the map data obtained in one of the thirdstep, the fifth step and the seventh step.